1. Field of the Invention
This invention relates to an apparatus for positioning a semiconductor device which apparatus is used in a field of production of semiconductor devices.
More particularly, the invention relates to a preliminary positioning apparatus for positioning a semiconductor wafer with efficiency and high accuracy on a semiconductor system when the semiconductor wafer is to be supplied to a semiconductor producing apparatus.
2. Prior Art
In production of semiconductor devices, positioning of a semiconductor wafer is important in a light exposure step, a line width measuring step, and so on. Normally, such positioning involves preliminary positioning (what is called prealignment) before a semiconductor wafer is fed to a light exposure apparatus, and final positioning (what is called final alignment) after the semiconductor wafer has been fed to the light exposure apparatus. In conventional preliminary positioning, a semiconductor wafer fed to a flat support plate is pushed and rotated by a few rollers located around an outer periphery of the semiconductor wafer while it is floated by air blown thereto. During such rotation of the semiconductor wafer, an orientation flat of the semiconductor wafer (a straight edge portion of a semiconductor wafer along which a circumferential edge of the semiconductor wafer is cut away) is detected, and then the orientation flat of the semiconductor wafer is contacted with a flat face of a positioning means thereby to position the semiconductor wafer.
After then, using a transporting means having a suitable means such as a vacuum attracting means, the semiconductor wafer is removed from the preliminary positioning support plate and placed onto a semiconductor wafer positioning stage, for example, of a light exposure apparatus. Then, the vacuum attracting means of the transporting means is rendered inoperative while the semiconductor wafer is attracted in position by another vacuum attracting means which may be provided on the positioning stage of the light exposure apparatus. However, in the case of delivery by air using such a vacuum attracting means, a semiconductor wafer is supported while it is slid by an air layer below. Accordingly, notwithstanding such preliminary positioning, there will often occur a displacement or dislocation of a semiconductor wafer when it is attracted to the transporting means or when it is transferred from the transporting means to the positioning stage.
Meanwhile, in such a conventional preliminary positioning apparatus, contamination of a semiconductor wafer is readily caused by a few rollers which contact with an outer periphery of a semiconductor wafer, and a sensor for detecting and a catcher for catching an orientation flat of a semiconductor wafer. Besides, such a conventional preliminary positioning apparatus requires a large number of components. Further, in case such components as described above which engage with a semiconductor wafer are abrased, the total amount of such abrasion will deteriorate accuracy in positioning a semiconductor wafer. In addition, while the conventional preliminary positioning apparatus is constituted such that a catcher for catching an orientation flat of a semiconductor wafer is brought into contact with a semiconductor wafer at a predetermined timing after the orientation flat of the semiconductor wafer has been detected, if the timing is missed or lost, the semiconductor wafer will stop at a position in which a portion thereof other than the orientation flat is contacted with the catcher, resulting in failure of positioning of the semiconductor wafer.
If a semiconductor wafer is transported to a positioning stage while accurate preliminary positioning is not attained in this manner, following problems will occur: final positioning of a semiconductor wafer requires much time; where final positioning is effected automatically, accuracy will not come within a range in which automatic positioning is allowed, resulting in failure in automatic final positioning of a semiconductor wafer; and the number of products per unit time (throughput) is reduced.